Allergies May Protect Against Brain Tumors

New research offers an upside to people living with allergies.

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MONDAY, August 6, 2012 — Allergies get a bad rap, but people who have them might actually reap a significant benefit — less risk of glioma, a tumor that starts in the brain.

New research adds scientific evidence to a body of self-reported studies suggesting a link between allergies and lower risk of brain tumors.

"People who have brain tumors have a lot fewer allergies than the people who do not have brain tumors," says Judith Schwartzbaum, PhD, an associate professor of epidemiology at Ohio State University in Columbus, Ohio, who led the study. "We didn't know which came first," she says. Brain tumors suppress your immune system, which could in turn suppress any allergic reactions had by the patients.

Dr. Schwartzbaum and her colleagues analyzed stored blood samples of 594 glioma patients, which they obtained from the Janus Serum Bank in Norway. The samples had been taken 20 years before the patients were diagnosed, which eliminated the question of which came first. The researchers found that those with allergy-related antibodies (proteins called IgE, or immunoglobulin E) had a nearly 50 percent lower risk of developing glioma compared to allergy-free patients.

How Would Allergies Protect You From Cancer?

"We don't know why we see this," Schwartzbaum says. But she has a couple of theories.

It could be that the immune system of a person with allergies is working harder, and as it defends the body against allergens, it also works against tumors. Another idea has to do with the blood-brain barrier, a barrier between the immune function cells and the brain.

"It's hard for immune cells to get into the brain because you wouldn't want to have inflammation in your brain. It's kind of protective," says Schwartzbaum. "But it's possible that a consequence of allergies is that this blood-brain barrier is more accessible to immune cells, and the immune system [in those people with allergies] can get rid of very small early tumors."

Her team's next step is to figure out why they see what they see. Then she hopes they can figure out how to prevent these tumors or who will get them.

What About Other Cancers?

"There was a bright idea that allergies would protect you against cancer, but that doesn't seem to work for most cancers. For brain tumors, however, the evidence is very consistent," Schwartzbaum says.

If Schwartzbaum's blood-brain barrier theory proves true, one could hypothesize that allergies let immune cells into the brain, thus preventing tumors like glioma, whereas other types of cancer may not get a similar benefit from the immune system. That's still something researchers need to figure out.

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